The principal aim of this project is to examine the influence of environmental and host factors prior to recruitment on the health performance and survival of recruits during military service. A second aim is the analysis of a random sample of volunteers and draftees who were rejected on the basis of an army medical examination. Early-age socioeconomic, ecological, anthropometric and biomedical variables will be used to determine predictors of the odds of rejection as well as to define the relationship between recruits and the entire male population of military age. Another aspect of this project is the development of measures of military stress as a possible predictor of morbidity and mortality at later ages. Such measures can be developed both from psychological information in medical reports and discharge papers and from information regarding exposure to battle conditions, confinement to prison, and other stress-inducing circumstances. A fourth task is the analysis of the factors affecting the immediate outcome (as opposed to late-age effects) of particular infections developed after induction into the Union Army, such as the case fatality rate of persons contracting measles while in the army. Other links between characteristics of the recruits and their service health histories that will be investigated include waiting-time to contract specific diseases; the number of repeated episodes of specific diseases; the probability of being discharged as a consequence of specific diseases; and the probability of entirely avoiding various diseases. Examination of health experiences during enlistment should serve to define certain conditions or combinations of conditions at earlier ages that made individuals prone to particular diseases during military service. Such information will also contribute to the identification of predictors of morbidity and mortality at middle and late ages.